Growth and structure of L1₀ ordered FePt films on GaAs(001)

The structural properties of epitaxial L1₀ ordered FePt(001) films, grown by molecular beam epitaxy (alternating deposition of Fe and Pt atomic layers) on buffer-Pt/seed-Fe/GaAs(001) have been studied by in situ reflection high-energy electron diffraction and by ex situ x-ray scattering as a function of the growth conditions. Reflection high-energy electron diffraction intensity oscillations measured during FePt layer growth provide evidence for island growth at T_s = 200^° C and quasi layer-by-layer growth at T_s = 350^° C. From small-angle and wide-angle x-ray scattering it was found that the degree of epitaxy depends critically on morphology of the seed layer and the substrate roughness. X-ray diffraction analysis showed that the long-range order parameter increases from near zero for films grown at 200^°C to 0.65 for films grown at 350^°C. This confirms the fact that the order parameter is mainly determined by the surface mobility of the atoms which is controlled experimentally by the substrate temperature.